The present invention relates to a method for recovering a metal and a reagent and kit for recovery of a metal for use in the same. The present invention also relates to a method for analyzing a metal and an analysis apparatus for use in the same.
It is known that metals such as mercury, cadmium, lead, and arsenic accumulate in human bodies, which results in adverse effects on health. Therefore, it is important to analyze metals in biological samples such as urine and the like and samples of food and beverage such as water and the like.
In analyzing a metal, generally, as a pretreatment, foreign substances are removed from a sample, a metal is separated from the resulting sample, and the separated metal is analyzed. In the pretreatment, a solvent extraction is widely used. The solvent extraction is a method in which a metal in a sample is extracted into an organic medium by utilizing the polarity of a chelating agent to be bound to the metal according to the difference in distribution coefficient of the metal to an aqueous medium and the organic medium. The metal can be further concentrated by evaporating the organic medium after the extraction. As a specific example of the solvent extraction, a dithizone method using, as the chelating agent, 1,5-diphenyl-3-thiocarbazone (hereinafter, also referred to as “dithizone”) that is insoluble in an aqueous medium under acidic conditions is defined in JIS, for example (see, Mercury Analysis Manual, Ministry of the Environment, March 2004, Japanese Patent No. 2969226). In the dithizone method, first, dithizone and a liquid sample such as urine are mixed under acidic conditions, and a complex between the dithizone and a metal present in the liquid sample is formed in the mixture. Subsequently, an organic medium such as carbon tetrachloride or chloroform is added to the mixture. Then, the complex is extracted into the organic medium because the distribution coefficient of the complex to the aqueous medium is different from that of the complex to the organic medium. Thereafter, this organic medium is recovered. Thus, the metal is recovered as the complex from the liquid sample. When the organic medium is evaporated, the metal can be further concentrated.
However, it is essential to use an organic medium in the conventional solvent extraction method as mentioned above. In the case of using an organic medium, handling thereof is complicated, and there is a risk that a waste liquid thereof affects the environment. Moreover, in order to concentrate the metal extracted using the organic medium, a decompressor for evaporating the organic medium is required, for example.